CN116500620A - Data processing method and device of millimeter wave radar, storage medium and unmanned vehicle - Google Patents
Data processing method and device of millimeter wave radar, storage medium and unmanned vehicle Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/88—Radar or analogous systems specially adapted for specific applications
- G01S13/93—Radar or analogous systems specially adapted for specific applications for anti-collision purposes
- G01S13/931—Radar or analogous systems specially adapted for specific applications for anti-collision purposes of land vehicles
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
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- G—PHYSICS
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- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
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Abstract
The invention provides a data processing method and device of millimeter wave radar, a storage medium and an unmanned vehicle, wherein the method comprises the following steps: obtaining an intermediate frequency signal according to the transmitting signal and the echo signal; processing the intermediate frequency signal to obtain a range-Doppler spectrogram; peak detection is carried out on the range-Doppler spectrogram, and the range and a plurality of Doppler frequencies of the corresponding target object are obtained according to the detection result; determining the Doppler frequency of a first transmitting antenna in the M transmitting antennas according to the distance and the Doppler frequencies on the distance Doppler frequency spectrogram, and constructing a spectrum matrix of the target object according to the Doppler frequency of the first transmitting antenna; and obtaining azimuth angle and pitch angle information of the target object according to the frequency spectrum matrix and a preset calibration matrix. The method can realize the efficient processing of the radar original data so as to quickly obtain the required frequency spectrum or point cloud information, and reduces the processing time and the calculation cost of the 4D millimeter wave radar data.
Description
Technical Field
The invention relates to the technical field of radars, in particular to a data processing method and device of a millimeter wave radar, a storage medium and an unmanned vehicle.
Background
With the development of the automobile industry, the automatic driving technology is mature, the dependence degree of intelligent vehicles on various sensor devices is higher, and the requirements on technical indexes of various vehicle body sensors are higher. The millimeter wave radar is used as an all-weather all-day sensor, has strong robustness to severe weather conditions and strong speed and distance measuring capability, and is an essential component on an automatic driving vehicle.
Because the angle resolution of the traditional 3D (speed, distance and azimuth) millimeter wave radar is very small, the target height information cannot be measured, and the problems of very sparse point cloud and the like cannot be truly applied to a sensing system of an unmanned vehicle.
With the rapid development of the radar field, the next generation of 4D (speed, distance, azimuth, pitch) millimeter wave radar can realize the imaging capability of high-resolution point cloud, and realize higher angular resolution in both azimuth and pitch. In addition, the 4D radar has the advantages of long detection distance, all-weather operation, low power consumption and low cost. Therefore, the 4D millimeter wave radar can complete the complementary effect on the laser radar and the camera, so that the fusion of the sensors realizes all-weather and remote environment perception.
Since the data acquired by the millimeter wave radar is the result of sampling the analog signal, the data processing needs to be performed on the radar signal in order to decouple the information such as the speed in the signal. Fig. 1 shows a data processing flow of a conventional single-input multiple-output (SIMO) radar system, including performing three FFTs (fast Fourier transform, fast fourier transforms) on a sampled ADC signal, including a distance FFT, a doppler FFT, and an angle FFT, to obtain a distance-angle-doppler spectrum, or performing peak detection on the distance-doppler spectrum obtained after two FFTs to obtain a target point, and then performing angle FFTs and angle estimation to obtain a point cloud.
However, for the 4D millimeter wave radar, in order to improve the angular resolution and obtain the pitch angle information, a multiple-input multiple-output (MIMO) radar system employing more antennas is required to obtain a larger virtual array, and as shown in fig. 2, a conventional MIMO radar system of three-transmit-four-receive, for example, includes 3 transmitting antennas 11 and 4 receiving antennas 12, and the 3 transmitting antennas 11 and 4 receiving antennas 12 may form a virtual antenna array 13 including 12 virtual receiving channels. Thus, a MIMO radar system can fill (interpolate) virtual array elements using a structured sparse matrix, in principle, such virtual array can be much larger than an array of an equivalent conventional system with the same number of antenna elements, and can have better spatial resolution at a smaller cost than an equivalent physical array antenna. However, the MIMO radar system inevitably increases the amount of data to be processed, and the increase in the amount of data also increases the processing power requirement, and if the conventional data processing flow is continued to be used, the time cost and the calculation cost will be greatly increased.
Accordingly, there is a need to provide an improved solution to overcome the above technical problems in the prior art.
Disclosure of Invention
In order to solve the technical problems, the invention provides a data processing method and device of a millimeter wave radar, a storage medium and an unmanned vehicle, which can solve the problems of long data processing time and high calculation cost of a 4D millimeter wave radar and can accelerate the application of a millimeter wave radar perception algorithm in the field of automatic driving.
According to a first aspect of the present invention, there is provided a data processing method of a millimeter wave radar including a virtual antenna array composed of M transmitting antennas and N receiving antennas, M and N each being a positive integer greater than 1, the data processing method comprising:
obtaining an intermediate frequency signal according to a transmitting signal of the millimeter wave radar and a received echo signal;
processing the intermediate frequency signal to obtain a range-Doppler spectrogram;
carrying out peak detection on the range-Doppler spectrogram, and obtaining the range and a plurality of Doppler frequencies of a corresponding target object according to the detection result;
determining the Doppler frequency of a first transmitting antenna in the M transmitting antennas according to the distance and the Doppler frequencies on the distance Doppler spectrogram, and constructing a spectrum matrix of the target object according to the Doppler frequency of the first transmitting antenna, wherein the phase shift of a transmitting signal of the first transmitting antenna relative to a reference transmitting signal is zero;
Obtaining azimuth angle and pitch angle information of the target object according to the frequency spectrum matrix and a preset calibration matrix,
the calibration matrix comprises a plurality of frequency spectrum matrices corresponding to a plurality of groups of azimuth angles and pitch angles.
Optionally, processing the intermediate frequency signal to obtain a range-doppler spectrum graph includes:
ADC sampling is carried out on the intermediate frequency signal to obtain a sampling signal;
windowing the sampling signal by using a Hamming window to obtain a windowed signal;
performing Fourier transform of a fast time dimension on the windowed signal to obtain a distance spectrogram;
and carrying out Fourier transformation of a slow time dimension on the range spectrogram to obtain the range Doppler spectrogram.
Optionally, peak detecting the range-doppler spectrogram includes:
constructing a detection window comprising a detection unit and a reference unit according to an average constant false alarm detection algorithm, and sliding the detection unit on the range-Doppler spectrogram to acquire a detection unit signal;
comparing the detection unit signal with a detection threshold, and judging that the detection unit is a target unit when the detection unit signal is larger than the detection threshold; otherwise, the detection unit is judged to be a noise unit,
Wherein the reference unit comprises a plurality of units surrounding the detection unit, and the detection threshold is the average value of all signal levels in the reference unit.
Optionally, before the detection window including the detection unit and the reference unit is constructed according to the average constant false alarm detection algorithm, the method further includes:
the range-doppler spectrum is reduced to one-nth on the doppler axis.
Optionally, obtaining the distance and the plurality of doppler frequencies of the corresponding target object according to the detection result includes:
acquiring coordinate information of the target unit in the range-Doppler spectrogram, wherein the coordinate information comprises range information and Doppler frequency information;
and calculating the Doppler frequencies according to the acquired Doppler frequency information and the phase shift relation between two adjacent transmitting antennas in the M transmitting antennas to obtain the distance and the Doppler frequencies corresponding to the target object.
Optionally, determining the doppler frequency of the first one of the M transmit antennas according to the distance and the plurality of doppler frequencies on the distance doppler spectrum graph includes:
determining a plurality of coordinate points on the range-doppler spectrogram according to the range and the plurality of doppler frequencies, and acquiring signal intensities of the plurality of coordinate points on the range-doppler spectrogram;
And respectively comparing the signal intensities of two adjacent coordinate points, and determining the Doppler frequency corresponding to the second coordinate point as the Doppler frequency of the first transmitting antenna when the difference value between the signal intensity of the second coordinate point and the signal intensity of the first coordinate point in the two adjacent coordinate points is larger than a preset value, wherein the Doppler frequency corresponding to the second coordinate point is larger than the Doppler frequency corresponding to the first coordinate point.
Optionally, constructing the spectrum matrix of the target object according to the doppler frequency of the first transmitting antenna includes:
calculating and obtaining M x N Doppler frequencies of the target object corresponding to each virtual receiving channel according to the phase shift relation of each virtual receiving channel in the virtual antenna array relative to the reference transmitting signal by taking the Doppler frequency of the first transmitting antenna as a reference value;
and arranging the obtained M-N Doppler frequencies according to a preset sequence, and constructing the spectrum matrix.
According to a second aspect of the present invention, there is provided a data processing apparatus of a millimeter wave radar including a virtual antenna array composed of M transmitting antennas and N receiving antennas, M and N each being a positive integer greater than 1, the data processing apparatus comprising:
The mixer is used for obtaining an intermediate frequency signal according to the transmitting signal of the millimeter wave radar and the received echo signal;
the range-Doppler spectrogram generation unit is used for processing the intermediate frequency signal to obtain a range-Doppler spectrogram;
the distance and speed information acquisition unit is used for carrying out peak detection on the distance Doppler frequency spectrogram and acquiring the distance and a plurality of Doppler frequencies of a corresponding target object according to the detection result;
a spectrum matrix construction unit, configured to determine, on the range-doppler spectrum graph, a doppler frequency of a first transmitting antenna of the M transmitting antennas according to the range and the plurality of doppler frequencies, and construct a spectrum matrix of the target object according to the doppler frequency of the first transmitting antenna, where a phase shift of a transmitting signal of the first transmitting antenna with respect to a reference transmitting signal is zero;
the azimuth angle and pitch angle information acquisition unit is used for acquiring azimuth angle and pitch angle information of the target object according to the frequency spectrum matrix and a preset calibration matrix, wherein the calibration matrix comprises a plurality of frequency spectrum matrixes corresponding to a plurality of groups of azimuth angles and pitch angles.
According to a third aspect of the present invention, there is provided a storage medium having stored therein a computer program which, when executed, implements a data processing method as described above.
According to a fourth aspect of the present invention there is provided an unmanned vehicle comprising a memory and a processor, the memory having stored therein a computer program which when executed by the processor implements a data processing method as described above.
The beneficial effects of the invention at least comprise:
according to the embodiment of the invention, the Doppler frequency of the first transmitting antenna in the M transmitting antennas is determined through the obtained range Doppler frequency spectrogram, and the spectrum matrix corresponding to the target object is constructed according to the Doppler frequency of the first transmitting antenna, so that the azimuth angle and pitch angle information of the target object can be obtained by searching the same spectrum matrix in the preset calibration matrix.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed.
Drawings
FIG. 1 illustrates a data processing flow of a conventional single-transmit multi-receive radar system;
FIG. 2 shows a schematic diagram of a conventional multi-transmit multi-receive radar system;
fig. 3 is a flow chart schematically showing a data processing method of a millimeter wave radar according to an embodiment of the present invention;
FIG. 4 is a flow chart of a method for obtaining a range-Doppler spectrum graph according to an embodiment of the present invention;
fig. 5 shows a schematic diagram of a peak detection method according to an embodiment of the present invention;
FIG. 6 is a flow chart of a method for obtaining range and Doppler frequencies of a target object according to an embodiment of the present invention;
FIG. 7 shows a schematic diagram of a two-dimensional Fourier transform process provided in accordance with an embodiment of the invention;
fig. 8 shows a schematic diagram of a detection window in constant false alarm detection according to an embodiment of the present invention;
figure 9 is a flow chart of a method for obtaining a doppler frequency of a first transmit antenna according to an embodiment of the present invention;
fig. 10 is a flowchart of a method for constructing a spectrum matrix according to an embodiment of the present invention;
fig. 11 shows a point cloud of a millimeter wave radar provided according to an embodiment of the present invention;
fig. 12 is a schematic diagram showing the structure of a data processing apparatus of a millimeter wave radar provided according to an embodiment of the present invention;
Fig. 13 shows a schematic structural diagram of an unmanned vehicle according to an embodiment of the present invention.
Detailed Description
In order that the invention may be readily understood, a more complete description of the invention will be rendered by reference to the appended drawings. Preferred embodiments of the present invention are shown in the drawings. The invention may, however, be embodied in different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Reference herein to "an embodiment" means that a particular feature, structure, or characteristic may be included in at least one implementation of the present application. In the description of the embodiments of the present application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" and "a second" may explicitly or implicitly include one or more such feature. Moreover, the terms "first" and "second," etc. are used to distinguish between similar objects and not necessarily to describe a particular order or sequence. It is to be understood that the data so used may be interchanged where appropriate such that the embodiments of the present application described herein may be implemented in other sequences than those illustrated or otherwise described herein. Furthermore, the terms "comprise" and "comprise," as well as any variations thereof, are intended to cover non-exclusive inclusion.
The millimeter wave radar has the advantages of miniaturization, low cost, long distance, large field angle FOV (field of view), high resolution and multifunction, is the development trend of the millimeter wave radar, and is also several aspects of competition among various large millimeter wave radar manufacturers.
Referring to fig. 3 to 10, fig. 3 is a flow chart of a data processing method of a MIMO millimeter wave radar according to an embodiment of the present invention. The MIMO millimeter wave radar comprises M transmitting antennas and N receiving antennas, wherein the M transmitting antennas and the N receiving antennas form a virtual antenna array comprising M x N virtual receiving channels, M and N are positive integers which are larger than 1, and M x N represents the product of M and N. The arrangement conditions of the transmitting antennas and the receiving antennas can be reasonably set according to actual conditions, and the arrangement conditions of the virtual receiving channels can also be reasonably set according to actual conditions.
By way of example, a data processing method of the MIMO millimeter wave radar will be described herein with only an example in which the MIMO millimeter wave radar includes 12 transmitting antennas (Tx 0 to Tx11, respectively) and 16 receiving antennas (Rx 0 to Rx15, respectively). All the transmitting antennas and the receiving antennas transmit and receive simultaneously, so that in order to construct each virtual receiving channel, the transmitting signals transmitted by the transmitting antennas Tx0 to Tx11 respectively can be obtained after the reference transmitting signals are phase-shifted through the phase shifter, the phase shift (i.e. the phase difference) of the transmitting signals of each transmitting antenna relative to the reference transmitting signals is different, but the phase shift between the transmitting signals of two adjacent transmitting antennas is 16 ω, ω is the angular frequency. For example, the phase shift of the transmission signal of the transmission antenna Tx0 with respect to the reference transmission signal is zero (the transmission signal of the transmission antenna Tx0 may also be directly taken as the reference transmission signal), the phase shift of the transmission signal of the transmission antenna Tx1 with respect to the reference transmission signal is 16 ω, the phase shift of the transmission signal of the transmission antenna Tx2 with respect to the reference transmission signal is 32 ω, … …, and so on, the phase shift of the transmission signal of the transmission antenna Tx11 with respect to the reference transmission signal is 176 ω; in addition, the echo signals received by the 16 receiving antennas also have a phase shift of 0 to 15 omega with respect to each of the transmission signals. Finally, the transmitted signals from the 12 transmit antennas will generate 192 echo signals with phases of [0, ω,2 ω,3 ω,4 ω,5 ω, …,191 ω ] at the 16 receive antennas, corresponding to 192 virtual receive channels in the virtual antenna array, equivalent to 1 transmit 192 receive.
As shown in fig. 3, the data processing method specifically includes the following steps:
in step S1, an intermediate frequency signal is obtained from the transmission signal of the millimeter wave radar and the received echo signal.
The received echo signals and the corresponding transmit signals are input into a mixer at each receive antenna, and a difference frequency signal, i.e. an intermediate frequency signal, is obtained by the mixer.
The mixer is an electronic component that can combine two signals together to generate a new signal with a new frequency. Wherein the instantaneous frequency of the mixer output signal is equal to the difference between the frequencies of the transmit signal and the echo signal, and the phase of the mixer output signal is equal to the difference between the phases of the transmit signal and the echo signal.
In step S2, the intermediate frequency signal is processed to obtain a range-doppler spectrum.
Referring to fig. 4, 7 and 8, in this embodiment, step S2 further includes the following steps:
in step S21, an ADC (Analog-to-digital converter) samples the intermediate frequency signal to obtain a sampled signal.
The intermediate frequency signals obtained at the respective receiving antennas are input to an analog-to-digital converter, and the respective intermediate frequency signals are converted from analog signals to digital signals. The intermediate frequency signal is complex, the ADC sampling of the intermediate frequency signal comprises the ADC sampling of the real part and the ADC sampling of the imaginary part, and the sampling results of the real part and the imaginary part are respectively stored into even number bits and odd number bits.
The ADC sampling of each intermediate frequency signal includes fast time sampling within each chirp pulse and slow time sampling in units of chirp pulses, as shown in fig. 7, with only the data processing at one receive antenna shown in fig. 7. Illustratively, the present embodiment is described with a fast time sampling number of 512 and a slow time sampling number of 256, that is, 512 data are sampled in each chirp pulse, and 256 chirp pulses are sampled consecutively.
Optionally, after sampling the intermediate frequency signal corresponding to each receiving antenna is completed, each sampling result may be spliced along the dimension of the receiving antenna to obtain an ADC tensor. The three dimensions of the ADC tensor are a fast time-sampling dimension, a slow time-sampling dimension, and an antenna dimension, respectively, and the size thereof is 512×256×16, for example.
In step S22, the sampling signal is windowed using a hamming window to obtain a windowed signal.
Due to the frequency spectrum leakage at signal truncation caused by the discontinuity of the sampling period, a windowing process is required for the discrete sampled signals before fourier transformation is performed.
By way of example, in this embodiment, the hamming window is used to window the sampled signal, where the attenuation of the main lobe peak and the first side lobe peak of the hamming window can reach 40db, so that the spectrum leakage can be effectively reduced.
In step S23, a fast-time fourier transform is performed on the windowed signal to obtain a distance spectrogram.
In step S24, a slow-time fourier transform is performed on the range-spectrogram to obtain a range-doppler-spectrogram.
The purpose of performing two-dimensional FFT in the fast and slow time dimensions on the windowed signal is to solve the problem of distance and velocity coupling of the target object, and the velocity and distance information can be decoupled by two fourier transforms in the fast and slow time dimensions, so as to obtain a range-doppler map (RD map).
In one possible example, the range-doppler spectrogram includes a range dimension, a doppler dimension, and an amplitude dimension. It can be understood that fig. 7 only illustrates the processing result of the data obtained at a certain receiving antenna in the MIMO millimeter wave radar after two fourier transforms in the distance dimension and the doppler dimension, so as to more clearly reflect the correspondence between the position of the target object in the range-doppler spectrum chart and the distance and doppler frequencies, and is not limited to the range-doppler spectrum chart related to the embodiment of the present invention.
In step S3, peak detection is performed on the range-doppler spectrum, and the range and the plurality of doppler frequencies corresponding to the target object are obtained according to the detection result.
It will be appreciated that the location of the peak in the range-profile and range-doppler profile directly corresponds to the location of the target object. Therefore, by performing peak detection on the range-doppler spectrum graph, range and doppler frequency information of the target object can be obtained, and speed information of the target object can be obtained according to the doppler frequency corresponding to the target object, and a specific calculation method can be understood according to the prior art, which is not described in detail herein.
It can be understood that the 12 transmission signals of the MIMO millimeter wave radar are signals of 12 different phases obtained by performing different degrees of phase shift on the reference transmission signal, so that, based on the correlation between the phases and the frequencies, in a range-doppler spectrum diagram obtained by performing FFT twice on the data sampled at each receiving antenna, a plurality of peak points with the same distance but different corresponding doppler frequencies appear for one target object. Therefore, when the peak value detection is performed on the range-doppler spectrogram, the range and the plurality of doppler frequencies corresponding to the same target object can be obtained according to the detection result, and the difference between two adjacent doppler frequencies in the obtained plurality of doppler frequencies is 16 units. It should be understood that although a plurality of doppler frequencies are obtained for the same target object, the obtained calculation results should be the same when calculating the velocity information of the target object from the plurality of doppler frequencies, respectively.
Further, referring to fig. 5, peak detection of the range-doppler spectrogram includes the steps of:
in step S31, a detection window including a detection unit and a reference unit is constructed according to an average constant false alarm detection algorithm, and the detection unit is slid on the range-doppler spectrogram to obtain a detection unit signal.
In step S32, the detection unit signal is compared with the detection threshold, and whether the detection unit signal is greater than the detection threshold is determined, if yes, step S33 is executed, otherwise, step S34 is executed.
In step S33, the detection unit is determined to be the target unit.
In step S34, the detection unit is determined to be a noise unit.
It will be appreciated that the range-doppler spectrum map reflects the power spectrum distribution of the environment and the target, but the clutter and noise have different interference levels in different scenarios, i.e. the interference power is variable, and the target object needs to be identified by using relatively accurate information of the target object, so that the detector needs to be designed to distinguish the target object from the background noise. Preferably, a two-dimensional constant false alarm detection (constant false alarm rate, CFAR) algorithm is selected to peak detect the range-doppler spectrogram, since there is some ambiguity in the signal corresponding to the target object in both the range and doppler dimensions. In addition, since the power of the back-shadow noise may vary with time, place, etc., it is not appropriate to set a fixed detection threshold when peak detection is performed.
In this embodiment, the MIMO millimeter wave radar uses CA-CFAR (cell averaging-constant false alarm rate) to determine the size of the detection threshold, and referring to fig. 8, when determining the size of the detection threshold, the spectrum area to be detected is divided into a plurality of cells 21, and each cell 21 is detected in turn. When each unit 21 is detected, the unit 21 is used as a detection unit 22, a detection window including the detection unit 22 and a reference unit 23 is constructed according to an average constant false alarm detection algorithm, each unit 21 in a spectrum area to be detected is traversed by sliding the detection unit 22 on a range-doppler spectrogram, and a detection unit signal and a detection threshold corresponding to each unit 21 are obtained. Wherein the detection unit 22 is the center of the detection window, and the reference unit 23 includes a plurality of units 21 surrounding the detection unit 22; the detection threshold in each detection window is the average value of all signal levels in the reference unit 23 or the product of the average value and the threshold factor, and the specific calculation method may refer to the method of calculating the detection threshold by CA-CFAR in the prior art, which is not limited in the embodiment of the present invention.
In some preferred embodiments, a protection unit may also be provided for the detection unit 21 in the constructed detection window to further ensure the accuracy of the detection result.
In the detection process, the method further includes comparing the detection unit signal (i.e. the power of the signal received in the detection unit) in each detection window with the corresponding detection threshold to determine whether the echo signal received in the detection unit 22 by the current receiving antenna in the MIMO millimeter wave radar is from the echo signal reflected by the target object. Specifically, when the detection unit signal is greater than the detection threshold, it may be determined that the current detection unit 22 is the target unit; otherwise, it may be determined that the current detection unit 22 is a noise unit.
Because the echo signals received by each receiving antenna correspond to 12 transmitting signals, in addition to the peak points actually corresponding to the target object can be obtained in the range-doppler spectrogram, other peak points can be obtained based on the phase shift relations of different transmitting signals. Thus in some preferred embodiments, to avoid interference with information detection of the target object due to phase shifts of the plurality of transmitted signals, prior to constructing a detection window comprising a detection unit and a reference unit according to an average constant false alarm detection algorithm, further comprising: the range-doppler spectrum is reduced to one-nth on the doppler axis. That is, the aforementioned spectrum region to be detected includes only the N-th region of the range-doppler spectrum, so that not only the accuracy of the detection result can be improved, but also the data processing amount can be reduced.
Further, referring to fig. 6, obtaining the distance and the plurality of doppler frequencies of the corresponding target object according to the detection result includes the following steps:
in step S35, coordinate information of the target unit in the range-doppler spectrogram is acquired, where the coordinate information includes range information and doppler frequency information.
In step S36, a plurality of doppler frequencies are calculated according to the acquired doppler frequency information and the phase shift relationship between two adjacent transmitting antennas of the M transmitting antennas, so as to obtain a distance corresponding to the target object and a plurality of doppler frequencies.
After the target unit of the target object is detected according to the average constant false alarm detection algorithm, the distance information and Doppler frequency information of the target object can be obtained by acquiring the coordinate information of the target unit in the distance Doppler frequency spectrogram. The coordinate information of the target unit on the distance dimension of the distance Doppler spectrogram is the distance information of the corresponding target object, and the coordinate information of the target unit on the Doppler dimension of the distance Doppler spectrogram is the Doppler frequency information of the corresponding target object.
Taking the range-doppler spectrum obtained at the receiving antenna Rx0 as an example, it can be seen from the foregoing description that the phase shift relationship between 12 transmission signals causes a plurality of peak points corresponding to the same target object to appear in the range-doppler spectrum, and the range information corresponding to the plurality of peak points is the same. After the distance information and the doppler frequency information of a group of corresponding target objects are obtained in the frequency spectrum region of 1/16 of the distance doppler spectrum chart in step S35, the phase shift or frequency shift relationship between the doppler frequencies corresponding to two adjacent peak points can be calculated according to the phase shift relationship between two adjacent transmitting antennas in the M transmitting antennas, so that a plurality of doppler frequencies corresponding to a plurality of peak points at the same distance can be calculated.
With continued reference to fig. 3, in step S4, a doppler frequency of a first one of the M transmit antennas is determined on the range-doppler-spectrum graph according to the range and the plurality of doppler frequencies, and a spectrum matrix of the target object is constructed according to the doppler frequency of the first transmit antenna.
In this embodiment, the first transmitting antenna of the M transmitting antennas refers to a transmitting antenna with a phase shift of the transmitting signal with respect to the reference transmitting signal of zero, that is, a transmitting antenna Tx0.
Referring to fig. 9, determining the doppler frequency of the first of the M transmit antennas based on the range and the plurality of doppler frequencies on the range-doppler spectrum graph comprises the steps of:
in step S41, a plurality of coordinate points are determined on the range-doppler spectrogram according to the range and the plurality of doppler frequencies, and signal intensities of the plurality of coordinate points on the range-doppler spectrogram are obtained.
In step S42, the signal intensities of the two adjacent coordinate points are compared, and when the difference between the signal intensity of the second coordinate point and the signal intensity of the first coordinate point in the two adjacent coordinate points is greater than a preset value, the doppler frequency corresponding to the second coordinate point is determined as the doppler frequency of the first transmitting antenna.
In one possible example of the present invention, the calculated 256/16=16 doppler frequencies are included in each range-doppler spectrogram, but only 12 doppler frequencies correspond to 12 transmission signals, and the signal intensities corresponding to the rest of the doppler frequencies are slightly weaker than the signal intensities corresponding to the 12 doppler frequencies. Based on this principle, in the range-doppler spectrum diagram corresponding to the receiving antenna Rx0, a plurality of coordinate points are determined at the distance corresponding to the target object according to each doppler frequency, and the signal intensity of each coordinate point is acquired in the amplitude dimension of the range-doppler spectrum diagram.
For example, the plurality of coordinate points are respectively marked as A0, A1, A2, A3, … and a15 in the order from small to large according to the corresponding doppler frequency, after the signal intensity of each coordinate point is obtained, the differences of the signal intensities of the coordinate point A1 and the coordinate point A0, the coordinate point A2 and the coordinate point A1, the coordinate point A3 and the coordinate points A2, …, the coordinate point a15 and the coordinate point a14 are respectively calculated, and when the difference of the signal intensity of a certain coordinate point and the signal intensity of the previous coordinate point adjacent to the certain coordinate point is greater than a preset value, the doppler frequency corresponding to the coordinate point can be determined as the doppler frequency of the first transmitting antenna (such as Tx 0).
Further, referring to fig. 10, constructing a spectrum matrix of the target object according to the doppler frequency of the first transmitting antenna includes the steps of:
in step S43, the doppler frequency of the first transmitting antenna is taken as a reference value, and m×n doppler frequencies of the target object corresponding to each virtual receiving channel are obtained by calculating according to the phase shift relationship between each virtual receiving channel in the virtual antenna array and the reference transmitting signal.
In step S44, the obtained m×n doppler frequencies are arranged according to a preset sequence, so as to construct a spectrum matrix.
In this embodiment, the doppler frequency of the first transmitting antenna corresponds to a virtual receiving channel formed by the transmitting antenna Tx0 and the receiving antenna Rx0, and if the phase of the reference transmitting signal in the MIMO millimeter wave radar is 0, the phase of the echo signal received by the virtual receiving channel is also 0.
Since the phases of the echo signals (or the phase shifts relative to the reference transmit signals) received at 192 virtual receive channels in the virtual antenna array are [0, ω,2 ω,3 ω,4 ω,5 ω, …,191 ω ], the doppler frequency of the first transmit antenna is used as the reference value, and 192 doppler frequencies of the target object corresponding to each virtual receive channel can be easily calculated according to the phase shift relationship of each virtual receive channel in the virtual antenna array relative to the reference transmit signals.
And rearranging the obtained 192 Doppler frequencies according to a preset sequence (such as an ascending sequence of the phase shift of the relative reference transmission signal), so as to construct and obtain a spectrum matrix corresponding to the current target object.
In step S5, azimuth and pitch angle information of the target object is obtained according to the spectrum matrix and a preset calibration matrix.
In this embodiment, the azimuth angle and the pitch angle of the target object are recovered through a pre-constructed calibration matrix, where a plurality of spectrum matrices are stored in the pre-constructed calibration matrix, and each spectrum matrix corresponds to a group of azimuth angle and pitch angle. When the azimuth angle and pitch angle information of the target object is obtained, the cross correlation relationship between the frequency spectrum matrix of the target object obtained in the step S4 and the calibration matrix can be directly utilized to recover the azimuth angle and pitch angle, namely, the frequency spectrum matrix of the target object obtained in the step S4 is used as a search condition to search the azimuth angle and pitch angle corresponding to the frequency spectrum matrix in the pre-constructed calibration matrix, so that the azimuth angle and pitch angle information of the target object is obtained.
For example, assuming that the MIMO millimeter wave radar is designed to require a maximum azimuth angle of 180 °, a maximum pitch angle of 12 °, a resolution of azimuth angle of 0.1 °, and a resolution of pitch angle of 1 °, a plurality of spectrum matrices corresponding to 1800×12 sets of azimuth angles and pitch angles need to be stored in a pre-built calibration matrix, and the size of the calibration matrix is 21600×192.
It should be noted that, for convenience of understanding, the foregoing embodiments of the present invention are merely exemplary illustrations of the data processing procedure when detecting a target object. However, it can be understood that, when multiple target objects need to be detected simultaneously, the data processing manner corresponding to each target object during detection can be executed with reference to the technical scheme disclosed in the present invention, and the technical scheme extended based on the manner still belongs to the technical scheme claimed in the present invention.
It should be understood that, the sequence number of each step in the foregoing embodiment does not mean that the execution sequence of each process should be determined by the function and the internal logic, and should not limit the implementation process of the embodiment of the present invention.
Illustratively, after the distance, speed, azimuth, and pitch angle information of each target is obtained, a point cloud data map may be obtained from the obtained distance and angle information of each target, as shown in fig. 11.
For example, when a range-azimuth map (RA map) needs to be constructed, since only the spectrum value of the target object in azimuth needs to be calculated, in step S5, only a plurality of spectrum matrices at the pitch angle of 0 ° may be selected to construct the calibration matrix, so that the data processing amount may be reduced when the azimuth information of the target object is acquired by calculating the cross-correlation.
In summary, compared with the prior art that three-dimensional Fourier transform is needed to perform angle estimation on a target, the method and the device can efficiently process the radar original signal into the required point cloud and spectrum signal by performing two-dimensional Fourier transform, and reduce the processing time and the calculation cost of radar data.
The embodiment of the invention also discloses a data processing device of the millimeter wave radar, as shown in fig. 12, the data processing device comprises: a mixer 31, a range-doppler spectrogram generation unit 32, a range and velocity information acquisition unit 33, a spectrum matrix construction unit 34, and an azimuth and pitch angle information acquisition unit 35.
Wherein the mixer 31 is configured to obtain an intermediate frequency signal from a transmission signal of the millimeter wave radar and a received echo signal.
The range-doppler spectrogram generation unit 32 is configured to process the intermediate frequency signal to obtain a range-doppler spectrogram.
The distance and velocity information obtaining unit 33 is configured to perform peak detection on the distance doppler spectrum graph, and obtain a distance and a plurality of doppler frequencies corresponding to the target object according to the detection result.
The spectrum matrix construction unit 34 is configured to determine a doppler frequency of a first transmitting antenna of the M transmitting antennas according to the distance and the plurality of doppler frequencies on the distance doppler spectrum chart, and construct a spectrum matrix of the target object according to the doppler frequency of the first transmitting antenna. Wherein the phase shift of the transmit signal of the first transmit antenna relative to the reference transmit signal is zero.
The azimuth and pitch angle information obtaining unit 35 is configured to obtain azimuth and pitch angle information of the target object according to the spectrum matrix and a preset calibration matrix. The calibration matrix stores a plurality of spectrum matrices corresponding to a plurality of groups of azimuth angles and pitch angles.
It should be noted that, the data processing device for millimeter wave radar provided by the embodiment of the present invention may be used to execute the data processing method for millimeter wave radar, so as to achieve the same beneficial effects as the data processing method in each embodiment. Further, it should be understood that, since the respective modules are merely set to illustrate the functional units of the apparatus of the present invention, the physical devices corresponding to the modules may be the processor itself, or a part of software in the processor, a part of hardware, or a part of a combination of software and hardware. Therefore, the number of individual modules in the data processing apparatus of the millimeter wave radar shown in fig. 12 is merely illustrative. Those skilled in the art will appreciate that the various modules in the apparatus may be adaptively split or combined. Such splitting or combining of specific modules does not cause the technical solution to deviate from the principle of the present invention, and therefore, the technical solution after splitting or combining falls within the protection scope of the present invention.
It will be appreciated by those skilled in the art that the present invention may implement all or part of the procedures in the methods of the above embodiments, or may be implemented by a computer program instructing relevant hardware, and the computer program may be stored in a computer readable storage medium, and the computer program may implement the steps of the respective method embodiments when executed by a processor. Wherein the computer program comprises computer program code, which may be in the form of source code, object code, executable files or in some intermediate form, etc. The computer readable storage medium may include: any entity or device, medium, usb disk, removable hard disk, magnetic disk, optical disk, computer memory, read-only memory, random access memory, electrical carrier wave signals, telecommunications signals, software distribution media, and the like capable of carrying the computer program code.
Still further, another aspect of the present invention provides a computer-readable storage medium having stored therein a computer program which, when executed by a processor, is capable of implementing the data processing method of the millimeter wave radar in any of the above embodiments. The computer readable storage medium may be a storage device including various electronic devices, and optionally, the computer readable storage medium in the embodiments of the present invention is a non-transitory computer readable storage medium.
Further, according to another aspect of the present invention, there is also provided an unmanned vehicle, as shown in fig. 13, the unmanned vehicle 4 including: a memory 41 and a processor 42, the memory 41 storing a computer program 411, the computer program 411 when executed by the processor 42 implementing the data processing method of the millimeter wave radar described in the above embodiment.
The unmanned vehicle can realize the data processing method of the millimeter wave radar in the embodiment, and achieves the same beneficial effects as the embodiment.
Finally, it should be noted that: it is apparent that the above examples are only illustrative of the present invention and are not limiting of the embodiments. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. And obvious variations or modifications thereof are contemplated as falling within the scope of the present invention.
Claims (10)
1. A data processing method of a millimeter wave radar, the millimeter wave radar including a virtual antenna array composed of M transmitting antennas and N receiving antennas, M and N each being a positive integer greater than 1, wherein the data processing method includes:
Obtaining an intermediate frequency signal according to a transmitting signal of the millimeter wave radar and a received echo signal;
processing the intermediate frequency signal to obtain a range-Doppler spectrogram;
carrying out peak detection on the range-Doppler spectrogram, and obtaining the range and a plurality of Doppler frequencies of a corresponding target object according to the detection result;
determining the Doppler frequency of a first transmitting antenna in the M transmitting antennas according to the distance and the Doppler frequencies on the distance Doppler spectrogram, and constructing a spectrum matrix of the target object according to the Doppler frequency of the first transmitting antenna, wherein the phase shift of a transmitting signal of the first transmitting antenna relative to a reference transmitting signal is zero;
obtaining azimuth angle and pitch angle information of the target object according to the frequency spectrum matrix and a preset calibration matrix,
the calibration matrix comprises a plurality of frequency spectrum matrices corresponding to a plurality of groups of azimuth angles and pitch angles.
2. The data processing method of claim 1, wherein processing the intermediate frequency signal to obtain a range-doppler spectrogram comprises:
ADC sampling is carried out on the intermediate frequency signal to obtain a sampling signal;
windowing the sampling signal by using a Hamming window to obtain a windowed signal;
Performing Fourier transform of a fast time dimension on the windowed signal to obtain a distance spectrogram;
and carrying out Fourier transformation of a slow time dimension on the range spectrogram to obtain the range Doppler spectrogram.
3. The data processing method of claim 1, wherein peak detection of the range-doppler spectrogram comprises:
constructing a detection window comprising a detection unit and a reference unit according to an average constant false alarm detection algorithm, and sliding the detection unit on the range-Doppler spectrogram to acquire a detection unit signal;
comparing the detection unit signal with a detection threshold, and judging that the detection unit is a target unit when the detection unit signal is larger than the detection threshold; otherwise, the detection unit is judged to be a noise unit,
wherein the reference unit comprises a plurality of units surrounding the detection unit, and the detection threshold is the average value of all signal levels in the reference unit.
4. The data processing method of claim 3, wherein before constructing a detection window including a detection unit and a reference unit according to an average constant false alarm detection algorithm, further comprising:
The range-doppler spectrum is reduced to one-nth on the doppler axis.
5. The data processing method according to claim 4, wherein obtaining the distance and the plurality of doppler frequencies of the corresponding target object according to the detection result comprises:
acquiring coordinate information of the target unit in the range-Doppler spectrogram, wherein the coordinate information comprises range information and Doppler frequency information;
and calculating the Doppler frequencies according to the acquired Doppler frequency information and the phase shift relation between two adjacent transmitting antennas in the M transmitting antennas to obtain the distance and the Doppler frequencies corresponding to the target object.
6. The data processing method of claim 5, wherein determining the doppler frequency of the first one of the M transmit antennas based on the range and the plurality of doppler frequencies on the range-doppler spectrogram comprises:
determining a plurality of coordinate points on the range-doppler spectrogram according to the range and the plurality of doppler frequencies, and acquiring signal intensities of the plurality of coordinate points on the range-doppler spectrogram;
and respectively comparing the signal intensities of two adjacent coordinate points, and determining the Doppler frequency corresponding to the second coordinate point as the Doppler frequency of the first transmitting antenna when the difference value between the signal intensity of the second coordinate point and the signal intensity of the first coordinate point in the two adjacent coordinate points is larger than a preset value, wherein the Doppler frequency corresponding to the second coordinate point is larger than the Doppler frequency corresponding to the first coordinate point.
7. The data processing method of claim 1, wherein constructing a spectral matrix of the target object from the doppler frequency of the first transmit antenna comprises:
calculating and obtaining M x N Doppler frequencies of the target object corresponding to each virtual receiving channel according to the phase shift relation of each virtual receiving channel in the virtual antenna array relative to the reference transmitting signal by taking the Doppler frequency of the first transmitting antenna as a reference value;
and arranging the obtained M-N Doppler frequencies according to a preset sequence, and constructing the spectrum matrix.
8. A data processing apparatus of a millimeter wave radar including a virtual antenna array composed of M transmitting antennas and N receiving antennas, M and N each being a positive integer greater than 1, wherein the data processing apparatus includes:
the mixer is used for obtaining an intermediate frequency signal according to the transmitting signal of the millimeter wave radar and the received echo signal;
the range-Doppler spectrogram generation unit is used for processing the intermediate frequency signal to obtain a range-Doppler spectrogram;
the distance and speed information acquisition unit is used for carrying out peak detection on the distance Doppler frequency spectrogram and acquiring the distance and a plurality of Doppler frequencies of a corresponding target object according to the detection result;
A spectrum matrix construction unit, configured to determine, on the range-doppler spectrum graph, a doppler frequency of a first transmitting antenna of the M transmitting antennas according to the range and the plurality of doppler frequencies, and construct a spectrum matrix of the target object according to the doppler frequency of the first transmitting antenna, where a phase shift of a transmitting signal of the first transmitting antenna with respect to a reference transmitting signal is zero;
the azimuth angle and pitch angle information acquisition unit is used for acquiring azimuth angle and pitch angle information of the target object according to the frequency spectrum matrix and a preset calibration matrix, wherein the calibration matrix comprises a plurality of frequency spectrum matrixes corresponding to a plurality of groups of azimuth angles and pitch angles.
9. A storage medium having stored therein a computer program which, when executed, implements the data processing method of any one of claims 1 to 7.
10. An unmanned vehicle comprising a memory and a processor, the memory having stored therein a computer program which, when executed by the processor, implements the data processing method of any of claims 1 to 7.
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| CN116840805A (en) * | 2023-08-30 | 2023-10-03 | 长沙莫之比智能科技有限公司 | Human vital sign detection method based on MIMO radar and beam forming |
| CN116840805B (en) * | 2023-08-30 | 2023-11-10 | 长沙莫之比智能科技有限公司 | Human vital sign detection method based on MIMO radar and beam forming |
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